Pow switching device with enhanced programming

ABSTRACT

A PCB motor controller comprises relays mounted on a PCB and interconnected to power traces in or on the PCB to receive incoming three-phase power and to output three-phase power to a motor. Control power traces in or on the PCB connect the relays to control circuitry, also mounted on the PCB. A power supply is mounted on the PCB and connected to the control circuitry to provide power for its operation and for switching of the relays. The relays are switched in accordance with a point-on-wave (POW) switching scheme, allowing for the use or relays and the PCB, which may not otherwise be suitable for motor control applications.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from and the benefit of U.S.Provisional Application Ser. No. 62/541,458, entitled “PCB MotorController with POW Switching,” filed Aug. 4, 2017, which is herebyincorporated by reference in its entirety.

BACKGROUND

The present disclosure relates generally to motor controllers, and moreparticularly to a motor controller that utilizes point on wave switchingand that may be configured on a circuit board implementation.

Many different configurations of devices have been developed forstarting and stopping motors, particularly those used in industrialapplications. Most such applications require three-phase power for ACinduction motors. The type of control provided may vary, but typicallyincludes so-called “across the line” starters, soft starters, and otherdevices that start and stop the motors under the command of a humanoperator or automation controllers.

Cost and complexity of such devices has tended to depend on the featuresprovided, the components utilized, and so forth. In recent years,so-called “hybrid” devices have been developed that reduce the packagesize, but are based on the use of solid-state switches, which can beexpensive and offer little further advancement in cost or packaging.

There is a need, therefore, for a new paradigm for motor controllersthat departs from conventional approaches and allows for market-changingproduct offerings while providing highly reliable devices adapted tomultiple motor applications.

BRIEF DESCRIPTION

The present disclosure describes systems and methods designed to addresssuch needs. In accordance with certain aspects of the disclosure, asystem comprises a printed circuit board having three phase conductorsfor conveying incoming three phase power from a source and foroutputting three phase power to a three-phase AC electric motor, a powersupply mounted on and electrically coupled to the printed circuit board,and control circuitry mounted on and electrically coupled to the printedcircuit board and receiving power from the power supply. Three singlepole relays are mounted on and electrically coupled to respective phaseconductors to receive the incoming power and to provide the outgoingpower when closed. The relays each have a direct current operator thatreceives control signals from the control circuitry to switch inaccordance with a point-on-wave switching scheme to close at desiredtimes of an AC waveform of the incoming power and thereby completecurrent carrying paths from the source through the power conductors tothe motor. The control circuitry is programmed to control switchingbased upon desired electrical switching angles between electricalparameters of the three phases of incoming power.

In accordance with another aspect, a system comprises a printed circuitboard having three phase conductors for conveying incoming three phasepower from a source and for outputting three phase power to athree-phase load, control circuitry mounted on and electrically coupledto the printed circuit board and receiving power from a power supply,and three single pole relays mounted on and electrically coupled torespective phase conductors to receive the incoming power and to providethe outgoing power when closed based upon signals from the controlcircuitry to power the load. In operation, the control circuitrycontrols switching of the relays based upon a selected one of aplurality of pre-programmed switching routines stored in memoryassociated with the control circuitry.

The disclosure also sets forth a system comprises a printed circuitboard having three phase conductors for conveying incoming three phasepower from a source and for outputting three phase power to athree-phase AC electric motor, a power supply mounted on andelectrically coupled to the printed circuit board, and control circuitrymounted on and electrically coupled to the printed circuit board andreceiving power from the power supply. Three single pole relays aremounted on and electrically coupled to respective phase conductors toreceive the incoming power and to provide the outgoing power whenclosed. The relays each have a direct current operator that receivescontrol signals from the control circuitry to switch in accordance witha point-on-wave switching scheme to close at desired times of an ACwaveform of the incoming power and thereby complete current carryingpaths from the source through the power conductors to the motor. Thecontrol circuitry is programmed to control switching based upon desiredelectrical switching angles between electrical parameters of the threephases of incoming power. And the control circuitry is configured toreceive a signal indicative of a frequency of incoming power and toalter switching timing based upon the switching angles and thefrequency.

DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a perspective view of an example PCB motor controller inaccordance with the present disclosure;

FIGS. 2A and 2B are diagrammatical overviews of an example PCB motorcontroller and connections in such a device in accordance with thepresent disclosure;

FIG. 3 is a diagrammatical view of example control circuitry for a PCBmotor controller of the previous figures;

FIGS. 4A-4C are graphical representations of example phase voltages andcurrents for a PCB motor controller during closing of switching devices;

FIG. 5 is a graphical representation of example disconnecting ofthree-phase power to a motor;

FIG. 6 is a perspective view of an example 5-relay PCB motor controller;

FIG. 7 is a diagrammatical illustration of the PCB motor controller ofFIG. 6;

FIG. 8 is a further diagrammatical illustration of a presentlycontemplated arrangement of a PCB with circuit components for compactand efficient motor control;

FIG. 9 is a graphically illustration of exemplary currents duringclosing of relays of certain PCB motor controllers and how control maybe additionally based on temperature of an operator coil;

FIG. 10 is a similar graphical illustration of exemplary currents duringopening of a relay of the device;

FIG. 11 is a graphical illustration of exemplary electrical angles forPOW closing of the relays;

FIG. 12 is a graphical illustration of exemplary electrical angles foropening of the relays;

FIG. 13 is a graphical illustration of certain exemplary effects oftiming in switching;

FIG. 14 is another graphical illustration of certain exemplary effectsof timing in switching;

FIG. 15 is a flow chart illustrating exemplary logic for switching therelays; and

FIGS. 16A-16D are illustrations of certain presently contemplatedpackaging and form factors for the PCB motor controllers.

DETAILED DESCRIPTION

FIG. 1 illustrates an example motor controller 10 that comprises aPCB-based contactor or relay structure and that utilizes POW switching.The controller 10 comprises a PCB 12 that supports the controllercomponents as discussed below, and that provides routing for power, dataand control signals during operation (eliminating or reducing the needfor other wiring or connections). The controller may be packaged in amanner that conforms to industry standards for automation devices ofthis type, and particularly for three-phase, 208, 230, or 460 VAC motorcontroller and starter applications. In the illustrated embodiment, thePCB and its mounted components are supported on a base 14 and will becovered by a housing or enclosure 16 that mates with the base. Manyvariations and specific arrangements may be envisioned by those skilledin the art, such as DIN rail mounted enclosures, enclosures adapted tobe mounted on or near the driven motor, enclosures adapted to be mountedwith other system components (e.g., in motor control centers), and soforth. However, it is contemplated that the embodiments illustrated maybe made smaller and lighter than existing motor controllers andstarters, at least in part due to the use of PCB-mounted relays incombination with POW switching that allows for the use of relays thatotherwise would be unsuitable for the motor control tasks described.

In the embodiment shown in FIG. 1, three relays 18, 20, and 22 aremounted to the PCB and are electrically coupled to other circuitcomponents through the PCB. In particular, as discussed below, therelays have control connections that permit them to be automaticallyopened and closed (i.e., their conductive state changed) by controlsignals applied through control connections. Each relay is thereforeconnected, through the PCB, to line-side terminals 24 that allow for thecontroller to be coupled to a source of three-phase power (e.g., fromthe power grid, a generator, or any other power source, and through anydesired upstream components or switchgear, such as fuses, disconnects,etc.).

A power supply, indicated generally by reference numeral 28, is alsocoupled to the PCB 12, and provides power for operation of controlcircuitry 30 through the PCB. As discussed below, the power supply,which may receive incoming power from one or more of the phases of powerprovided through the terminals 24, may convert the incoming power toregulated power (e.g., DC power) used by the control circuitry formonitoring, computing, and control functions, including signals appliedto the relays 18, 20, and 22 to change their state. Three-phase power isthen output by the relays via load-side terminals 32, also through thePCB. The connections to the relays themselves may be through pins ortabs 34 provided in and extending from the packaging of the relays,which enter into and are electrically coupled to vias or holes 36 in thePCB (e.g., by soldering). Through operation of the power supply, thecontrol circuitry, and ultimately the relays, three-phase power isreceived by the controller, its application to a motor 38 is controlledthrough POW switching.

The relays may be of any suitable type and construction, though it ispresently contemplated that off-the-shelf, commercially available relaysmay be used that are ordinarily not rated for motor control, or forinrush currents that would ordinarily be experienced in three-phasemotor control applications. As will be appreciated by those skilled inthe art, in such applications, upon initial application of power to themotor and as the motor is brought up to its rated speed, inrush currentsmany times the rated currents may be encountered. The relays employed onthe present PCB-based controller may be ordinarily rated for otherapplications, but it has been found that they may operate, receive, andprovide power for motor starting and control by appropriate switching inaccordance with a POW scheme as outlined below. Example relays may berated for switching currents of at most 16 A (or 20 A) at 250 VAC,although other ratings may, of course be used. The relays may bepre-packaged subassemblies each having a housing with bottom-extendingcontacts mounting on the printed circuit board to receive the controlsignals, to receive the incoming power, and to output the outgoingpower. In some embodiments, each of the relays may have a weight of atmost about 15 grams, and a packaging or enclosure of no larger thanabout 45 mm long by 15 mm wide by 30 mm tall. Such relays arecommercially available from many sources, such as Finder of Almese,Italy under the commercial designation “45 series”, and Omron of Kyoto,Japan under the commercial designation G2RL.

FIG. 2A illustrates the PCB-based motor controller 10 in a schematicrepresentation. Here again, the illustrated embodiment comprises threerelays 18, 20, and 22, coupled to control circuitry 30 and thereby to apower supply 28. To provide the three-phase incoming power to therelays, conductive traces 40 are provided in or on the PCB and betweenthe input terminals 24 and the relays. Similarly, conductive traces 42are provided in or on the PCB between the output terminals 32 and therelays. The traces may be made by conventional PCB manufacturingtechniques (e.g., plating, etching, layering, drilling, etc.).

Each relay may be an electromechanical device that completes a singlecurrent carrying path (and interrupt the path) under the control of anelectromagnetic coil structure. In the illustration of FIG. 2A, themajor components of the relays are illustrated as including a contactsection 44 and a DC operator 46. The contact section may typicallycomprise at least one movable contact and at least one stationarycontact (while the representation of FIG. 2A shows a double-breakimplementation, in practice the relays may have a single movablecontact). The movable contact is displaced under the influence of amagnetic field created by energization of a coil of the operator viacontrol signals provided by the control circuitry. Each relay may alsocomprise a current sensor 48 that allows for detection of currents ofthe incoming (and/or outgoing) power. In some embodiments, the currentsensor may be a separate component that is associated with the tracesthat provide power from the line-side terminals to the relays (or thatprovide power from the relays to the load-side terminals). The currentsignals are used to control POW switching of the relays as discussedbelow. As also shown in FIG. 2A, conductive traces 50 are provided in oron the PCB to electrically couple the operators of the relays to thecontrol circuitry. These traces will typically be differently sized andspaced than the power traces 40 and 42 owing to the lower voltage andcurrent levels of the control signals. Finally, traces 52 will beprovided in or on the PCB to allow power to be provided between thepower supply 28 and the control circuitry. It should be noted that insome embodiments, additional monitoring, programming, datacommunication, feedback, and so forth may be performed by the componentsof the PCB-based motor controller, and in such cases, all signals may beprovided and exchanged by additional conductive traces formed in or onthe PCB.

FIG. 2B is another schematic diagram of the relays of the PCB-basedmotor controller. In this view, the relays 18 20, and 22 are shown asthey might be placed and coupled to the PCB. Control pins 54 are shownthat would be electrically coupled (e.g., soldered) to the controltraces of the PCB (or to plated vias, for example, in electricalcontinuity with the traces). Within the relays, the pins are coupled toeither side of a control coil 56 of the respective operator. These coilsare electromagnetically linked to the contacts as discussed above, whichare, in turn, coupled to power pins 58. Here again, the power pins willbe electrically coupled (e.g., soldered) to the power traces of the PCB(or to plated vias, for example, in electrical continuity with thetraces). It may be noted that the relays in certain presentlycontemplated embodiments are single-pole, single-throw devices for theirsimplicity and cost-effectiveness.

As noted above, the use of off-the-shelf relays that would otherwise beunderrated for and unsuitable for motor control applications is affordedby POW switching under the control of the control circuitry. FIG. 3illustrates certain components of the control circuitry. As shown, thecontrol circuitry comprises one or more processors 60 that, inoperation, execute programmed instructions for monitoring the incomingpower (and where desired the outgoing power), and based upon timingdeveloped from such monitoring, issues signals to control energizationof the relay coils. The programming code executed by the processor willtypically be stored in memory circuitry 62. The memory circuitry may beof any suitable types, and multiple memories may be used when desired.Among the programming code and data stored in the memory circuitry willbe configuration programming and parameters 64, such as electricalangles for switching, timing parameters, set points, and so forth.Control programming 66 for POW control of the relays is also stored inthe memory and executed by the processor. One or more interfaces 68 maybe provided, such as for the exchange of signals with the sensors(including, where necessary for digitization of the signals), withexternal components and circuits (such as for programming, monitoring,reporting, etc.), with the relay coils (for providing the powersignals), and so forth. The control circuitry will be provided withconductors or “pinouts” for communicating with such other devices viathe conductive traces of the PCB. In the illustration of FIG. 3, theseinclude conductors 70 for receiving sensor (e.g., current sensor) data,conductors 72 for exchanging data with a programming or communicationsinterface (e.g., in the event the controller is equipped for suchcommunication), and conductors 74 for providing the control signals tothe relays.

For the POW control, the control circuitry programming allows formonitoring of one or more characteristics of one or more of the phasesof the incoming power, and then for causing switching of the relaysbased upon timing developed from such monitoring. For example, it may beadvantageous to close (or “make”) two of the relays at or near a desiredphase-to-phase voltage relationship (e.g., peak) of incoming power. Theother relay may be closed (“made”) at a desired time thereafter. Suchswitching will reduce transient characteristics that could otherwiseoccur and that might overpower the relays. To allow for controlledswitching of the relays, the control signals may be DC signals (that is,not relying upon a sinusoidal waveform for application of power to theoperators). For opening (“breaking”) the relays, a similar POW schememay be used, in which one of the relays is first opened based upontiming developed from monitoring of the current for that phase, such asbased on a zero-crossing, and thereafter the other phases are opened.

To help illustrate, closing the switching devices to provide three-phaseelectric power to the motor is illustrated in FIGS. 4A-4C. FIG. 4Aillustrates the voltage of three-phase electric power (e.g., a firstphase voltage curve 76, a second phase voltage curve 78, and a thirdphase voltage curve 80) provided by a power source. FIG. 4B illustratesthe line to neutral voltage supplied to each terminal (e.g., firstterminal voltage curve 82, second terminal voltage curve 84, and thirdterminal voltage curve 86) of the motor. FIG. 4C illustrates linecurrent supplied to each winding (e.g., first winding current curve 88,second winding current curve 90, and third winding current curve 92) ofthe motor. As described above, the waveforms depicted in FIGS. 4A-4C maybe determined by control circuitry based on measurements collected bythe sensors.

As depicted, between t0 and t1, electric power is not connected to themotor. In other words, all of the relays are open. At t1, one or morerelays are closed to start current flow from the power source in twophases to the motor. To minimize inrush current and/or currentoscillations, a first phase and a second phase are connected based upona predicted or sensed timing as determined from the monitored waveforms.Accordingly, as depicted in FIG. 4A, the first phase and the secondphase are connected when the line-to-line voltage of the first phase(e.g., first phase voltage curve 76) and the second phase (e.g., asecond phase voltage curve 78) is at a maximum. Once connected, thefirst phase of the electric power flows into the first winding of themotor, the second phase of the electrical flows into the second windingof the motor, and the third winding of the motor is at an internalneutral (e.g., different from line neutral), as depicted in FIG. 4B.Additionally, since the two phases are connected at a predicted orsensed point, the current supplied to the first winding (e.g., firstwinding current curve 88) and the second winding (e.g., second windingcurrent curve 90) start at zero and gradually increase, as depicted inFIG. 4C, thereby reducing magnitude of in-rush current and/or currentoscillations supplied to the first and second windings.

After the first two phases are connected, at t2, the remaining relay isclosed to connect a third phase of the electric power to the motor.Similar to the first phase and the second phase, to minimize inrushcurrent and/or current oscillations, the third phase is also connectedbased upon a predicted current zero-crossing. Accordingly, as depictedin FIG. 4A, the third phase is connected when sum of line-to-linevoltage between the first phase (e.g., first phase voltage curve 76) andthe third phase (e.g., third phase voltage curve 80) and theline-to-line voltage between the second phase (e.g., second phasevoltage curve 78) and the third phase (e.g., third phase voltage curve80) is at a maximum (e.g., a predicted current zero-crossing), whichoccurs when the line-to-line voltage between the first phase and thesecond phase is at a minimum and third phase is at a maximum.

It should be noted that although the third phase is depicted as beingconnected at the first such subsequent occurrence, the third phase mayadditionally or alternatively be connected at any subsequent occurrence,for example at t3. Once connected, the third phase of the electric powerflows into the third winding of the motor, as depicted in FIG. 4B.Additionally, since the third phase is connected based upon a predictedcurrent zero-crossing, the third winding current 92 gradually changesfrom zero, as depicted in FIG. 4C, thereby reducing magnitude of in-rushcurrent and/or current oscillations supplied to the third winding.

Additionally, as described above, controlling the breaking (e.g.,opening) of the one or more switching devices may facilitate reducinglikelihood and/or magnitude of arcing, which may strain and/or wearcontacts and conductive structures in the relays and/or other connectedcomponents. As such, the one or more relays may be controlled such thatthey break based at least in part on a current-zero crossing (e.g.,within a range slightly before to at the current zero-crossing acrossthat relay).

To help illustrate, opening the switching devices to disconnectthree-phase electric power from an motor is described in FIG. 5. Morespecifically, FIG. 5 depicts the current supplied to the windings (e.g.,first winding current curve 88, second winding current curve 90, andthird winding current curve 92) of the motor. As described above, thewaveform depicted in FIG. 5 may be determined by control circuitry basedon measurements collected by the sensors.

As depicted, prior to t4, electric power is connected to the motor. Inother words, all of the relays are closed. At t5, one or more of therelays are opened to disconnect the third phase of the electric powerfrom the motor. As described above, to minimize arcing, the third phaseis disconnected based at least in part on a current zero-crossing in thethird phase. Accordingly, as depicted, the third phase is disconnectedwhen the current supplied to the third winding (e.g., third windingcurrent curve 92) is approximately zero. Once disconnected, the currentsupplied to the second winding current the first winding current adjustto the removal of the third phase.

After the third phase is disconnected, the remaining relays are openedto disconnect the other two phases (e.g., the first phase and the secondphase) of electric power to the motor at t6. Similar to disconnectingthe third phase, to minimize arcing, the first phase is disconnectedbased at least in part on a current zero-crossing in the first phase andthe second phase is disconnected based at least in part on a currentzero-crossing in that phase. Accordingly, as depicted, the first phaseand the second phase are disconnected when current supplied to thesecond winding (e.g., second winding current curve 90) and the firstwinding (e.g., first winding current curve 88) are approximately zero.Once disconnected, the electric power supplied to the motor begins todecrease. It should be noted that although the first phase and thesecond phase are depicted as being disconnected at the first subsequentcurrent zero-crossing, the first and second phases may additionally oralternatively be disconnected at any subsequent current zero-crossings.

In addition to the three-relay motor controller discussed above,PCB-based motor controllers with POW switching schemes, according to thepresent disclosure, may be designed for a number of alternativeapproaches to motor starting and control. For example, 5, 6, 8, 9, andother numbers of relays may be mounted on and controlled via traces inthe PCB for specific types of switching. FIGS. 6 and 7 illustrate anexample of a 5-relay PCB-based motor controller 94 with POW switching,such as may be used for wye-delta starting and control. In theembodiment of FIG. 6, the PCB 12 supports and is interconnected to theoriginal three relays discussed above that receive power from theline-side terminals and associated power traces in or on the PCB.However, here two additional relays 96 and 98 are provided that are alsoconnected to power traces in or on the PCB. FIG. 7 illustrates anexample how such interconnections of the relays may be made. As shown,relays 18, 20 and 22 are connected to power traces 40′, 40″ and 40′″,respectively to receive three-phase power from the line-side terminals.Here, however, while the input to relay 18 is connected to the inputpower trace 40′, its power output is connected to the output of relay 96by a jumper trace 100, which is also connected to the power output trace32′ (which would in turn be coupled to one of the load-side terminals).The input of relay 20 is connected to the input power trace 40″, whileits output is connected via a jumper trace 102 to the input of relay 96and to the output of relay 98. The jumper trace 102 is also connected tothe power output trace 32″. Finally, the input of relay 22 is connectedto the input power trace 40′″, while its output is connected to a thirdjumper trace 104 and to a third power output trace 32′″. Thisarrangement allows for wye-delta POW switching by appropriate control ofopening and closing of the five relays. An example of such switching isprovided, for example, in U.S. published patent application no.2016/0133413, which is hereby incorporated into the present disclosureby reference, in its entirety.

There are a number of enhancements and unique circuit layouts that maybe considered for packaging and interconnection of the components of PCBmotor controllers in accordance with the present techniques. FIG. 8illustrates an example layout for a PCB motor controller utilizing POWswitching. As in the earlier illustrations, the circuit board isindicated by reference numeral 12, and the relays by 18, 20, and 22,respectively, for each phase of power. The power is channeled to therelays via line traces 40 formed in or on the PCB, and power is provideddownstream for the motor via load traces 42. Here the contacts areillustrated at 44, and the illustrated relays each comprise a singlemovable contact that mates with a single stationary contact, althoughmultiple parallel contacts could be used. The operator for each relay ishere again indicated by reference numeral 46. Also, as in earlierillustrations, the processing circuitry for control of the relays isillustrated by reference numeral 60, and its associated memory byreference numeral 62. Interface circuitry for communicating with othercomponents and local and remote devices is indicated by referencenumeral 68.

In this embodiment, voltages are sensed for two of the phases ofincoming power, which might be referred to here as ϕA and ϕB. A voltagesending/zero cross detection circuit 106 is coupled to traces that tieto the incoming power traces for these phases. In practice, all threevoltages may be measured, although in the illustrated embodiment, and asdescribed more fully below, the switching may based upon aphase-to-phase voltage difference that is determined by circuit 106.Similarly, the current of at least one phase of power is measured by acurrent sensing circuit 108. In the illustrated embodiment, only onephase current, ϕC is measured. In other embodiments more or all of thecurrents may be measured, and in some cases, all phases may be monitoredtogether (e.g., for detection of faults, short circuits, etc.). Themeasured values are applied to the processing circuitry 60 (e.g., in rawform for digitization in the processor or associated circuitry, ordigitized by analog-to-digital converters, not separately shown). Asdiscussed below, closing of the switches may be based, for example, onthe phase-to-phase voltage determined by circuit 106, while openingtimes may be based upon the phase current measured by circuit 108.

In the embodiment illustrated in FIG. 8, simplicity is further enhancedby reducing the number of driver circuits used to power the operators ofthe relays. In this case, a first driver 110 powers relays 20 and 22 forϕA and ϕB. This is possible because the POW switching scheme calls forthese relays to be switched at the same time, closing before the thirdphase, and opening after the third phase. A separate driver 110′ isprovided for ϕC.

Also illustrated in FIG. 8 are one or more temperature sensors 112 thatmay optionally be placed on, in, or near the relays. These sensors maymeasure temperature of one or more of the switching devices, andparticularly to provide some indication of heating of the operator coil.Signals from the one or more temperature sensors may be received andprocessed by the processing circuitry to adjust power applied to therelays, such as to provide uniform timing of switching despite changesin temperature, as described below. FIG. 8 also shows power supplies,including a coil power supply 114, which may provide a standard voltagelevel for switching (e.g., 12 volts), as well as a low voltage powersupply 116, such as for powering the processor and any logic circuitsrequiring power.

FIGS. 9 and 10 illustrate currents that may be experienced by the relaycoils during closing and opening, respectively. In FIG. 9 the closingcurrent 120 is shown over time along axis 122. The current trace 124 mayinclude an initial increase shown to the left, followed by a decrease toa local dip 126. As indicated by time 128 for the solid trace 130, at anormal or reference temperature of the relay coil, the lowest point inthis dip may correspond to contact of the pole faces of the relay(confirming closing of the contacts slightly before that time).Thereafter the current will rise until it reaches as steady state level,as indicated at reference numeral 130. In a currently contemplatedembodiment, a relatively elevated voltage may be initially applied(e.g., 15 volts) to cause the relay to rapidly (and consistently) close,with a smaller current (e.g., 8 volts) being applied thereafter forholding the relay closed. These signals may be pulse width modulatedwhere desired, but in present embodiments, the operators of the relaysare provided with DC power to predictably control the timing of theiroperation.

The dashed trace 132 in FIG. 9 indicates different behavior of the relaydue to heating of the operator coil. In general, the electricalproperties of the coils may be affected by the temperature (e.g.,resistance). This may cause the dip in current, corresponding to theclosing of the relay, to shift, as indicated by time 134, and may alsoalter the initial and steady state current levels, as indicated by thearrows in FIG. 9. To counter such effects and to provide more consistentoperation despite temperature changes, the input signals may be alteredto raise (or lower) the currents and/or voltages applied, therebymaintaining the timing for closing at a stable location in time. Thismay be performed, for example, based on the sensed temperature of one ormore of the relay coils, or of a temperature in some way related to orindicative of the coil temperature, and then applying a computed orstored relationship with the desired current and/or voltage inputs(e.g., a coil voltage and temperature or resistance relationship storedin a lookup table).

FIG. 10 shows a similar effect during opening. Here, the coil current138 is again shown against time on axis 140. The current trace 136 shownin solid may represent the coil current at a nominal or referencetemperature. The opening may be considered to occur at a time 142. Asthe coil is heated or cooled, the electrical properties and thus thecurrent (for a given input signal) may here again change, as indicatedby the dashed trace 144. Without compensation this may change the timeof opening, as indicated at 146. To counter such effects, the inputsignals may be changed based upon sensed temperature to provide moreuniform timing for opening.

In certain currently contemplated embodiments, POW switching allows forthe use of smaller relays (and other components) than would be possibleif POW switching were not used. Benefits of such switching includegreatly reduced nefarious transitory effects on the controlled motor, aswell as greatly reduced arcing and consequent degradation of thecontacts of the relays. Tests have shown that a surprisingly extendedlife and numbers of cycles may be achieved even for relays not otherwiserated for such applications, largely due to maintaining POW switching.

FIGS. 11-14 illustrate some of the aspects of POW switching useful forthe PCB implementations contemplated here. In these embodiments, twoelectrical angles may be considered, a first, α, represents a point on aphase-to-phase voltage curve (that is the relative line voltage betweenϕA and ϕB in this case), while angle β represents a time thereafter. Onclosing, for the desired POW switching, energization of the relays forϕA and ϕB is controlled by selecting a desired angle α for closing bothrelays for those two phases of power, and an angle β for closing therelay for ϕC. This is illustrated in FIG. 11. The phase-to-phase voltage150 is shown against time on axis 152. The electrical angle α is hereselected at a maximum phase-to-phase voltage occurring at a timecorresponding to 90 electrical degrees in the voltage relationship (thatis, α equals 90 degrees), as indicated by reference numeral 154. Theangle β is then chosen for closing the third phase of power, ϕC, asindicated by reference numeral 156. It is believed that the optimalelectrical angle α for control of an induction motor is 90 degrees,while the optimal angle β for an induction motor is 90 degrees.

FIG. 12 illustrates a current waveform for the third phase, here ϕc,used as a basis controlling opening of the relays. Here, the current 160is shown against time 162. At a point 164 in advance of the current zerocrossing, the relay for ϕC is commanded to open. Then at an angle βthereafter, the other phases, ϕA and ϕB, are commanded to open, asindicated at time 166. In other words, on closing represents the angleafter desired time for closing the third phase, ϕC, after closing of thefirst two phases, ϕA and ϕB, while upon opening, β represents the angleafter the opening of the third phase, ϕC, that the other phases, ϕA andϕB, are opened. In presently contemplated embodiments, and for inductionmotors, it is believed that for POW opening, an optimal angle α foropening the third phase, ϕC, will correspond to a zero crossing of thecurrent for that phase (when the phase-to-phase voltage angle betweenthe other phases, ϕA and ϕB, will be approximately 75 degrees), with theoptimal timing for β, then being 90 degrees later (although in practicethe timing may be programmed without actively monitoring thephase-to-phase voltage).

Several points are of interest, however. First, these angles are subjectto considerable tolerance, as discussed above, while still providinggreatly enhanced performance as compared to conventional “non-POW”switching. Indeed, as noted, the use of even somewhat less than optimalPOW switching enables the use of a PCB arrangements of the typedescribed.

Secondly, the desired angles α and β may not be the same for differenttypes of loads, and it is contemplated that different switching timingmay be used for such different types of load. For example, an inductionmotor may have different characteristics than a capacitive load (e.g., acapacitor bank) (and in some cases inertial loads may differ fromnon-inertial loads). It is contemplated that such differences may betaken into account by appropriately adjusting the angles α and β. Insuch cases, the load may be characterized automatically or manually uponinstallation or commissioning of the PCB motor controller, and thedesired angles α and β applied via appropriate code in the programmingstored in memory and implemented by the processing circuitry. By way ofexample, it may be considered that nominal switching angles α and β forclosing the relays for switching inductive loads may be 90 degrees and90 degrees, respectively, while the angles may be 0 degrees and 90degrees, respectively, for resistive and capacitive loads.

Still further, to provide the desired switching timing with respect topoints in the voltage and current waveforms, the timing for applicationof control signals may be adjusted to anticipate these points. Someempirical testing will likely be in order for different relays (andcircuit layouts) to obtain the advance in the timing desired. Oncedetermined, control may follow based upon the desired angles and thedetermined advance in the timing. Of course, other adjustments, such asfor temperature as discussed above, may be implemented for furtherrefinement and consistency in the timing for opening and closing of therelays. However, for example, it is believed that although the anglesfor switching, and the implied timing, may be pre-selected andprogrammed, the actual timing may be dependent upon the tolerances,timing, performance, and su forth of the components and circuitsutilized in particular applications.

As noted, a substantial enhancement in performance may be obtained bytargeting the angles α and β (adjusted and where desired for certaincharacterized components and circuits) with some considerable tolerancein the “tightness” (precision and accuracy) of the actual moments ofopening and closing. For example, FIG. 13 shows a relationship betweenthe angles α and β along axes 168 and 170, respectively for closing therelays for an inductive load, such as an induction motor. It may benoted that the zones 172 and 174 represent regions of enhancedperformance, in this case determined based upon torque ripple of aninduction motor for one phase of power upon closing. In this example,zone 172 generally surrounds a “best” combination of angles α to β of 90electrical degrees to 90 electrical degrees, while zone 174 iseffectively a cyclic repeat of the relationship at 90 degrees and 270degrees, respectively. However, the zones appear to permit considerabletolerance in the timing. In practice, additional degradation inperformance could be seen at additional zones surrounding these.

For other loads, the relationships may be considerably different. Forexample, FIG. 14 shows favored timing for switching of one phase in thecase of a capacitive load, here with α along axis 180, and β along axis182. The more favored timing is here represented by zones 184 and 186.However, here again considerable tolerance is seen. Also, the cyclicoccurrence of the “best” zones for switching may allow for switching inthe very next cycle, or waiting for such favored zones in later cycles(that is, the angles may be delayed by intervals of 180 degrees. It mayalso be noted that, depending upon the angles selected, adjustments maybe made for component and circuit differences based upon theircharacterization.

But it should be noted that both for opening and closing of the relays,tolerance in the “best” electrical angles may be permitted. It shouldalso be noted that again for both opening and closing, it may be quiteuseful to characterize the loads being switched, and to then judiciouslyselect the angles α and β accordingly. Further by the use of such POWswitching, as noted above, relatively smaller devices, with lower movingmasses and thus lower inertias may be used, providing faster and morepredictable operation, reducing arcing and degradation, and enhancingperformance.

As a further enhancement and similarly to characterization of the load,in general it may be useful to characterize the electrical source aswell. For example, to provide a more universal product, the frequency ofthe line waveforms may be selected upon installation or commissioning(e.g., manually) or may be sensed by monitoring the voltage and/orcurrent waveforms. For example, at least two different frequencies maybe anticipated, 50 Hz and 60 Hz. The timing for switching may bedetermined by algorithms implemented by the processing circuitryaccordingly. Other frequencies may occur in other contexts, for examplein vehicles or generator-produced power. It may be noted, however, thatby selecting timing based upon the angles α and β, the appropriatetiming will nevertheless be determined based on these angles despite theuse of different input power frequencies.

Still further, it is believed that substantial improvement in life ofthe components, and particularly of the contacts of the relays (or othertypes of switching devices if used) may be obtained by monitoring of thepolarity of one or more of the phases of power, and controllingswitching based upon the monitored polarity. In particular, it isbelieved that the polarity of the power for each phase may affect thetype, direction, and effects of arcs that may develop during switching,and thereby the degradation that may take place in the relays, andparticularly in the stationary and movable contacts. To improveoperation over time, then, the polarity (that is, the polarity of thewaveform at the approach to switching) of one or more of the phases ofpower may be monitored, and from time to time this may be reversed byappropriate control of the switching timing. At some points duringoperation, then, one or more of the phases of power may be switched whenapproaching a desired voltage and/or current relationship with or from afirst polarity (e.g., a phase-to-phase voltage peak, currentzero-crossing, etc.) from a positive polarity or side of thecorresponding waveform, and then the same phase or phases may beswitched from the opposite, negative polarity or side of thecorresponding waveform. This alternation in polarity of switching may bedone based upon, for example, counting of switching events and notingfrom at which polarities the switches have been closed or opened.

FIG. 15 illustrates exemplary control logic 188 for certain operationsof the PCB POW motor controller. The logic may be considered in certainphases or groups of operations, including an installation or programmingor commissioning phase 190, a closing or power application to load phase192, and an opening or power interruption phase 194. In thecommissioning phase, 190, the load (and components and circuits) may becharacterized, as indicated at operation 196. As noted above, this mayinvolve selection from one of several possible pre-set options, such asfor induction motors, capacitive loads, and so forth. Though notseparately shown, this characterization may also involvecharacterization of the source power parameters (e.g., frequency). Basedupon the characterization, then, the desired angles and times forswitching may be computed, accessed (e.g., from a remote or onboardstorage) as indicated by operation 198, and loaded for use indetermining best switching times for POW operation. Where desired,certain parameters, including an indication of relay or coil temperaturemay be sensed as indicated by operation 200.

Then the relays of the device may be closed, based upon the desired POWswitching times in phase 192. For this, as noted above, voltages of atleast two phases may be monitored at operation 202, and in particular aphase-to-phase voltage is monitored between the two phases to be closedfirst. Optionally, at operation 204, the current of the other phase (orof more than one phase) may be monitored (although this may initially beonly for fault detection insomuch as before any connections are made nocurrent should flow). It may be noted that in practice, all of these maybe cyclically sensed and monitored so that the opening and closing mayoccur within a very brief delay after a command is issued by an operatoror control circuitry for operation of the relays. Moreover, the timingor determined signals to be applied to one or more of the relay coilsmay be adjusted at operation 206, such as based on the relay or coiltemperature. Then at operation 208, the relays for the first two phasesof power are closed, followed by the third phase, all based upon thedetermined POW timing. Where desired, the relay coil voltage may bereduced as indicated at operation 210 to reduce heating of the relays(and improve opening of the relays).

It should be noted that while FIG. 15 illustrates operation of only 3relays, as noted above, a number of other relays may be mounted on andelectrically controlled on the PCB, such as for wye-delta starting of amotor. When such relays are included, more complex closing and openingof the relays may be implemented at operation 208 to transition toapplication of power to the load.

As noted at operation 212, then, temperature can again be sensed forcontinued updating or correction of the relay switching timing, and sothat the controller is continuously able to determine this timing is ifa new switching command is received.

The controlled load should then be in steady state operation. At somepoint a command is received, from an operator or control circuitry, forinterrupting power to the load in phase 194. As noted above, opening ofthe relays may be based upon the current sensed for the phase to beopened before the other two, so that this current is sensed andmonitored at operation 214. The voltage of the other phases may, ofcourse be monitored at operation 216, as mentioned above, although thismay simply be optional at this point in the operation. Then at operation218 the timing may again be adjusted, such as for the current relay orcoil temperature. At operation 220, then, the third phase of power isinterrupted by opening the corresponding relay, followed by opening ofthe other two. Of course, if special switching schemes are implemented,such as wye-delta or other sequences, the opening (and closing) of therelays present on the PCB may be controlled accordingly at operation220.

It may be noted that a number of physical packaging options and formatsmay be envisioned, such as depending upon such factors as the downstreammarket, the products that the PCB controller may replace, the productsin which it may be incorporated, and so forth. FIGS. 16A-16D show just afew examples of such packaging. In the illustration of FIG. 16A, the PCBmotor controller is packaged in an enclosure 222 that may correspond toa form factor of a standard circuit breaker (e.g., with a standard 22 mmwidth 224). Such enclosures may be designed for mounting on standard DINrails 226. In another example of FIG. 16B, the enclosure 228 may mimic astandard contactor package with a similar wiring layout, and alsomountable on a DIN rail. Other embodiments may be designed for OEMmarkets, as shown in FIG. 16C. In such applications, one or more PCBmotor controllers 232 and 234 may be mounted on a single PCB 230, andthis may be designed to be integrated into OEM cabinets or productsalong with other automation or switchgear components. Due to the natureof the PCB design, a motor controller could, in this manner, be createdon a common circuit board with other circuits, such as for the controlof specific OEM machines. Still further, as shown in FIG. 16D, thepackaging may conform to formats for other automation devices, such asin this case a safety PLC packaging 236.

While only certain features of the invention have been illustrated anddescribed herein, many modifications and changes will occur to thoseskilled in the art. It is, therefore, to be understood that the appendedclaims are intended to cover all such modifications and changes as fallwithin the true spirit of the invention.

1. A system comprising: a printed circuit board having three phaseconductors for conveying incoming three phase power from a source andfor outputting three phase power to a three-phase AC electric motor; apower supply mounted on and electrically coupled to the printed circuitboard; control circuitry mounted on and electrically coupled to theprinted circuit board and receiving power from the power supply; andthree single pole relays mounted on and electrically coupled torespective phase conductors to receive the incoming power and to providethe outgoing power when closed, the relays each having a direct currentoperator that receives control signals from the control circuitry toswitch in accordance with a point-on-wave switching scheme to close atdesired times of an AC waveform of the incoming power and therebycomplete current carrying paths from the source through the powerconductors to the motor; wherein the control circuitry is programmed tocontrol switching based upon desired electrical switching angles betweenelectrical parameters of the three phases of incoming power.
 2. Thesystem of claim 1, wherein a first angle comprises an angle of aphase-to-phase voltage of two phases of the incoming power.
 3. Thesystem of claim 2, wherein a second angle comprises an anglerepresentative of occurrence of an electrical event after the firstangle.
 4. The system of claim 3, wherein the electrical event comprisesa current zero-crossing.
 5. The system of claim 1, comprising at leastone sensor coupled to sense a parameter indicative of temperature orheating of at least one of the relays or a component thereof, andwherein the control circuitry is programmed to alter at least one of theangles or a timing based upon at least one of the angles based upon thesensed parameter.
 6. The system of claim 1, wherein the first and secondangles are approximately 90 electrical degrees.
 7. The system of claim1, wherein timing of closing the relays is based upon a frequency of theincoming power and upon the first and second angles.
 8. The system ofclaim 7, wherein the frequency of incoming power is sensed by thesystem.
 9. A system comprising: a printed circuit board having threephase conductors for conveying incoming three phase power from a sourceand for outputting three phase power to a three-phase load; controlcircuitry mounted on and electrically coupled to the printed circuitboard and receiving power from a power supply; three single pole relaysmounted on and electrically coupled to respective phase conductors toreceive the incoming power and to provide the outgoing power when closedbased upon signals from the control circuitry to power the load; andwherein, in operation, the control circuitry controls switching of therelays based upon a selected one of a plurality of pre-programmedswitching routines stored in memory associated with the controlcircuitry.
 10. The system of claim 9, wherein different ones of thepre-programmed switching routines are adapted for switching differenttypes of loads.
 11. The system of claim 10, wherein the different typesof loads include an inductive load and a capacitive load, and whereinrespective switching routines for the inductive load and the capacitiveload are based upon different timing of switching.
 12. The system ofclaim 11, wherein the different timing of switching is based upondesired electrical angles of a point-on-wave switching scheme.
 13. Thesystem of claim 11, wherein the different timing of switching is basedupon a sensed frequency of the incoming power.
 14. A system comprising:a printed circuit board having three phase conductors for conveyingincoming three phase power from a source and for outputting three phasepower to a three-phase AC electric motor; a power supply mounted on andelectrically coupled to the printed circuit board; control circuitrymounted on and electrically coupled to the printed circuit board andreceiving power from the power supply; and three single pole relaysmounted on and electrically coupled to respective phase conductors toreceive the incoming power and to provide the outgoing power whenclosed, the relays each having a direct current operator that receivescontrol signals from the control circuitry to switch in accordance witha point-on-wave switching scheme to close at desired times of an ACwaveform of the incoming power and thereby complete current carryingpaths from the source through the power conductors to the motor; whereinthe control circuitry is programmed to control switching based upondesired electrical switching angles between electrical parameters of thethree phases of incoming power; and wherein the control circuitry isconfigured to receive a signal indicative of a frequency of incomingpower and to alter switching timing based upon the switching angles andthe frequency.
 15. The system of claim 14, wherein, in operation, thecontrol circuitry controls switching of the relays based upon a selectedone of a plurality of pre-programmed switching routines stored in memoryassociated with the control circuitry and based upon the frequency. 18.The system of claim 15, wherein different ones of the pre-programmedswitching routines are adapted for switching different types of loads.19. The system of claim 18, wherein the different types of loads includean inductive load and a capacitive load, and wherein respectiveswitching routines for the inductive load and the capacitive load arebased upon different timing of switching.
 20. The system of claim 19,wherein the different timing of switching is based upon desiredelectrical angles of the point-on-wave switching scheme.